BrainStuff Classics: Why Are Some Sea Turtles Hatching Almost All Female?

A sea turtle's sex is determined by the temperature where it hatches, and the Great Barrier Reef is warmer than ever before. Learn what this could mean in today's classic episode of BrainStuff, based on this article: https://science.howstuffworks.com/environmental/earth/oceanography/sea-turtles-great-barrier-reef-turning-99-percent-female.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff production of I Heart Radio. Hey
brain Stuff, I'm more in vogel Bomb and this episode
is a classic from our archives. Over the past few years,
we've all seen changes to expected weather patterns. There have
been more hurricanes in some areas, more droughts, and others
warmer winters. Here in Atlanta, where we produce this show,

(00:23):
some of these effects of climate change are pretty obvious,
but this episode is about one that's more subtle, if
just as big, the difference in how some sea turtles
are being born. Hey brain stuffling vocal bomb here. Australia's
Great Barrier Reef is an enormous climate change experiment that's
not happening in the safe isolation of a laboratory. Instead,

(00:45):
the warming waters off the east coast of the continent
have a profound real world effect on thousands of miles
of coral as well as the animals that live there.
For decades, scientists have suspected that increases in ocean's temperatures
would affect sex ratios in certain animals, and rese it
shows that's exactly what's happening to the Pacific Green sea turtles.
In most of Earth's creatures, gender is determined during the

(01:06):
fertilization process. That's not true of animals like turtles, crocodiles,
and alligators, though, which rely on a concept called temperature
dependent sex determination, or TDS to dictate the sex of
their offspring. In the case of turtles, warming waters and
sands are altering the TDS process During the breeding season.
The turtles, which can grow to nearly five hundred pounds

(01:27):
that's about two kims, with a shell diameter of four
feet or one point two meters, flop ashore and bury
their eggs in the sand. The temperature of that sand
determines whether baby turtles will wind up with blue or
pink flippers. Figuratively speaking, if the incubation temperature is below
eighty two degrees fahrenheit or thirty degrees celsius, the turtles
will hatch as males. Above eighty eight degrees fahrenheit or

(01:49):
thirty one degree celsius, the babies will be female. A
similar problem has been reported in loggerhead turtles on Florida beaches,
since scientists have noticed a strong bias toward female turtles
in some instances. Up to to see how varying temperatures
might affect turtle populations. Scientists compared sex ratios of turtles
near multiple breeding grounds around the Great Barrier Reef. They

(02:11):
used blood tests and laparro scopy to determine the sex
of these animals. At the southern edge of the reef,
near Brisbane, water temperatures are cooler and female turtles outnumber
males by a ratio of two to one, about sixty
five to sixty nine percent female. However, about one thousand,
two hundred miles north, in the largest and most critical
sea turtle rookery in the Pacific Ocean, warmer sea and

(02:31):
air temperatures are having a dramatic effect of hatchlings are female.
Although each male can mate with more than one female
during a breeding season, a severe imbalance in sex ratios
doesn't bode well for temperature sensitive species like sea turtles. Furthermore,
once the incubating sand becomes too warm, it outright kills
the developing organism, further threatening turtle populations. The study was

(02:53):
published in January eighteen in the journal Cell Biology. The
researchers write, our study highlights the need for immediate management
strategies aimed at lowering incubation temperatures at key rookeries to
boost the ability of local turtle populations to adapt to
the changing environment and avoid a population collapse or even extinction.

(03:16):
Today's episode was originally produced by Tristan McNeil and is
based on the article of Great Barrier Reef Green sea
turtles are hatching female on how stuff works dot Com,
written by Nathan Chandler. Brain Stuff is production of I
Heart Radio in partnership with how stuff works dot Com
and is produced by Tyler Clang. Four more podcasts my
heart Radio, visit the heart Radio app, Apple Podcasts, or

(03:37):
wherever you listen into your favorite shows.